The Environmental Protection Agency will join a probe by North Carolina’s environmental agency of how Duke Energy handled and maintained its coal ash across the state.

The public role of EPA so far has been in overseeing the response and cleanup of Duke’s Feb. 2 ash spill into the Dan River. A federal grand jury met this week in Raleigh to investigate a “suspected felony” surrounding the spill.

The state Department of Environment and Natural Resources has cited Duke for two violations at its Dan River power plant but not yet imposed fines. DENR also filed violations against five other Duke plants.

Secretary John Skvarla mentioned a “difficult and complicated” enforcement case that involves Virginia, where the Dan flows, in asking EPA to join the probe March 14.

“People should interpret this as DENR and EPA thinking this is a very important issue and that we want to bring all our resources to bear in determining a solution,” DENR spokesman Drew Elliott said Friday.

The state and EPA share joint authority for enforcing the federal Clean Water Act on rivers and lakes. EPA does not regulate groundwater, which has been contaminated at all 14 of Duke’s North Carolina coal plants, while the state does.

EPA, in turn, has expertise in investigating coal ash spills. That’s based on the massive 2008 spill of ash slurry by the Tennessee Valley Authority in eastern Tennessee.

It’s not clear whether EPA’s involvement would raise the likely penalties to Duke for the spill or its other ash operations.

“How we go about enforcement would very much depend on what we find in our investigation,” Elliot said.

Frank Holleman, senior attorney with the Southern Environmental Law Center, said the EPA’s involvement in the case should help ensure tougher enforcement. The center represents environmental groups that are parties to four state lawsuits against Duke.

“But the proof will be in the outcome,” he said by email. “To date, EPA has not been involved in the civil enforcement against Duke’s illegal coal ash pollution, although its criminal investigators have been actively working on the issues.”

The law center suggested DENR had previously tried to keep EPA out of its ash cases.

It released an email from a DENR official who wrote in March 2013 that EPA was poised to start investigating contamination at Duke’s Asheville power plant. EPA indicated it would not intervene, the official wrote, if the state instead took action.

“Great news!” Secretary Skvarla responded.

The law center filed notice it would sue Duke over the Asheville plant in January 2013. DENR filed its own lawsuit in March of that year.

Agreement at issue

DENR also said Friday it wants to pull out of a proposed agreement with Duke over contamination at the Riverbend and Asheville power plants.

The agreement, which called for a $99,000 fine of Duke and more study of groundwater contamination, drew a harsh public response when it was proposed last summer. Nearly all of about 5,000 public comments called it too lenient.

Public pressure and legal opinion against the deal has only intensified since the Dan River spill. Environmental groups claim the settlement showed collusion between Duke and DENR.

“We are happy they have abandoned the sweetheart settlement. The sad part is we’ve lost a year while they pursued it, and meanwhile we’ve had two failures” of Duke’s ash ponds, Holleman said. Duke this week reported a crack in a dam at its Cape Fear power plant southwest of Raleigh.

DENR said the terms of the agreement were based on the department’s long-standing interpretation of groundwater rules, which a Wake County judge overturned March 6.

Superior Court Judge Paul Ridgeway decided that the rules required “immediate action” to clean up the ash-tainted groundwater that’s been found at all 14 of Duke’s North Carolina coal plants.

Duke said last week that it plans to move all the ash from Riverbend, which borders Charlotte’s water source of Mountain Island Lake. City officials are reviewing Duke’s request to move the 2.7 million tons of ash held in ponds to Charlotte’s airport.